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The Coalsack (#308) is huge...6x4 degrees. The largest field-of-view of Slooh's telescopes that can image the Coalsack is only 42x42 arcminutes (.7x.7 degrees). That means that many exposures need to be taken and assembled into a mosaic. The mosaic of the Coalsack was assembled from 36 images taken with Slooh's Chile2 Wide-Field telescope. The imaging information is shown to the right.
The mosaic was assembled using version 2.04 of MicroSoft Image Composite Editor.
The MicroSoft ICE jpg image was post-processed with PhotoShop utilizing curves to stretch to bring out the brighter and darker areas.
Acrux (alpha Crux) is the bright star in the 4th image. The brightness caused direct problems with the 4th image (CS 14) and the 9th image (CS 23). They in turn caused secondary issues in assembling the rest of the mosaic. Any exposure that controls magnitude .76 Acrux prevents other stars from being captured successfully compared to all the other images. Conversely anything that duplicates the rest of the field to match all the others "blows" out Acrux AND causes flare problems in the surrounding frames. One area where that causes a problem is frame CS 23 where a large dark region is compromised.
Imaging Information for all frames:
Telescope: Chile2 Wide-Field
Camera: FLI PL 16803
FOV: 43x43 arcminutes
Image scale: 1.89 arcsec/pixel
Exposure: 1x50 sec L, 1x25 sec RGB
Filters: LRGB
Binning: 3x3
An example where an exposure that holds Acrux doesn't display many other field stars.
Note: The OP's coordinates for the Coalsack are pretty far away from those presented in SkySafari and Stellarium.
That made me wonder how much further to the left the dark nebulae extended. I googled Coalsack and found a good picture from Astronomy magazine. It is below.
It is nine degrees between the NGC at the top left of the Coalsack and zeta Crux below and to the left of Acrux.
Using the plate solved image and what I'd call the approximate center for the Coalsack gives coordinates of
Center RA: 12:48:42 Center Dec: -62:54:40
From SkySafari: 12:49:59.71 -62:38:53.3
Stellarium: 12:50:02.15 -62:29:52.5
Those are all long way away from
Bambury List: 12:31:19, -63:44:36
My mosaic: 12:28:32, -64:37:50
This is a small version of the 36 frame mosaic using Microsoft Image Composite Editor (Microsoft ICE). A larger version is at the bottom of this page. The bright star at the top of the image is Acrux. The second brightest star is zeta Crux on the right. The star just above the center of the frame is HD 110772.
Dark nebulae can be seen to the left (east) of the Acrux, but not so much to the right (west).
Using nova.astrometry.net on the mosaic gives:
Center (RA, hms): 12h 28m 31.615s
Center (Dec, dms): -64° 37' 50.075"
Size: 3.5 x 3.37 deg
Comparing my image center to where the Bambury OP's are can be seen in the image below. The tiny circle below the coordinates printed on the image is Bambury's.
My center is a degree lower than the coordinates from the Bambury program's: 12h 31m 19.0s, -63d 44m 36s but the RAs are 3 minutes. That makes me think that even centered on Bambury's, most of the dark nebulae would on more images to the left.
Plate solving this image shows
Center (RA, hms): 12h 53m 23.799s
Center (Dec, dms): -61° 20' 59.540"
Size: 18.2 x 15.7 deg
The Coalsack is huge. For reference, Acrux (to the right of the center) is the brightest star in the frame. NGC 4609 is in the upper left corner of my mosaic while it can be seen almost in the center in the Astronomy magazine picture. Looking at Acrux and NGC 4609's positions, it is pretty clear that my mosaic only captures the right and bottom parts of the Coalsack. The coordinates for the Coalsack given in the list and are close to Acrux are definitely much too far to the west.
Data for the 36 images in the first Coalsack mosaic
Name RA Dec Date Time
CS 11 12.68881 -63.16748 2/27/2024 3:30 UT
CS 12 12.60413 -63.16748 2/27/2024 3:40 UT
CS 13 12.51945 -63.16748 2/27/2024 3:45 UT
CS 14 12.43477 -63.16748 2/27/2024 3:50 UT
CS 15 12.35009 -63.16748 2/27/2024 4:15 UT
CS 16 12.26542 -63.16748 2/28/2024 6:20 UT
CS 21 12.69309 -63.74081 2/28/2024 6:40 UT
CS 22 12.60670 -63.74081 2/28/2024 6:45 UT
CS 23 12.52031 -63.74081 2/29/2024 6:55 UT
CS 24 12.43392 -63.74081 2/28/2024 7:10 UT
CS 25 12.34752 -63.74081 2/28/2024 2:45 UT
CS 26 12.26113 -63.74081 2/28/2024 2:50 UT
CS 31 12.69757 -64.31414 2/28/2024 2:55 UT
CS 32 12.60939 -64.31414 2/28/2024 3:05 UT
CS 33 12.52120 -64.31414 2/28/2024 3:45 UT
CS 34 12.43302 -64.31414 2/29/2024 2:05 UT
CS 35 12.34483 -64.31414 2/29/2024 2:10 UT
CS 36 12.25665 -64.31414 2/29/2024 2:15 UT
CS 41 12.70227 -64.88748 3/01/2024 3:45 UT
CS 42 12.61220 -64.88748 2/29/2024 2:25 UT
CS 43 12.52214 -64.88748 3/01/2024 1:30 UT
CS 44 12.43208 -64.88748 3/01/2024 1:35 UT
CS 45 12.34202 -64.88748 3/01/2024 1:40 UT
CS 46 12.25196 -64.88748 3/01/2024 1:45 UT
CS 51 12.70719 -65.46081 3/2/2024 1:40 UT
CS 52 12.61516 -65.46081 3/2/2024 1:45 UT
CS 53 12.52313 -65.46081 3/2/2024 1:50 UT
CS 54 12.43110 -65.46081 3/2/2024 2:10 UT
CS 55 12.33906 -65.46081 3/2/2024 2:15 UT
CS 56 12.24703 -65.46081 3/5/2024 5:15 UT
CS 61 12.71236 -66.03414 3/5/2024 5:20 UT
CS 62 12.61826 -66.03414 3/5/2024 5:40 UT
CS 63 12.52416 -66.03414 3/5/2024 5:30 UT
CS 64 12.43006 -66.03414 3/5/2024 6:45 UT
CS 65 12.33596 -66.03414 3/5/2024 6:50 UT
CS 66 12.24186 -66.03414 3/5/2024 7:45 UT
The images for the first Coalsack mosaic are below
Coordinates for the mosaic in grid format:
A B C D E F
1 12.68881 -63.16748 12.60413 -63.16748 12.51945 -63.16748 12.43477 -63.16748 12.35009 -63.16748 12.26542 -63.16748
2 12.69309 -63.74081 12.60670 -63.74081 12.52031 -63.74081 12.43392 -63.74081 12.34752 -63.74081 12.26113 -63.74081
3 12.69757 -64.31414 12.60939 -64.31414 12.52120 -64.31414 12.43302 -64.31414 12.34483 -64.31414 12.25665 -64.31414
4 12.70227 -64.88748 12.61220 -64.88748 12.52214 -64.88748 12.43208 -64.88748 12.34202 -64.88748 12.25196 -64.88748
5 12.70719 -65.46081 12.61516 -65.46081 12.52313 -65.46081 12.43110 -65.46081 12.33906 -65.46081 12.24703 -65.46081
6 12.71236 -66.03414 12.61826 -66.03414 12.52416 -66.03414 12.43006 -66.03414 12.33596 -66.03414 12.24186 -66.03414
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